Mucolipidosis Type IV Natural History Study

This study is a retrospective natural history study of MLIV. It involves the collection of all participants medical records prior to the date of consent. First, the study will provide an approximate description of the international MLIV population, which could inform the feasibility and design of interventional trials. Second, the results will be used to create an MLIV specific developmental timeline (akin to the Denver Developmental Screen (Frankenburg and Dodds, 1967)) against which a patient's developmental trajectory pre- and post-treatment can be compared. Third, the study will assess the reliability and validity of the GMFCS and our MLIV specific scales when applied retrospectively. These scales could provide longitudinal, quantitative historical data on the level of function and disability in MLIV patients. The scales could be used as endpoints in future trials or provide historical context for interpretation of treatment effects. Fourth, the study will define the rate of visual decline in patients, which could be halted by gene therapy targeted to the retina. Fifth, the study will analyze the natural history of MLIV associated EEG and brain MRI abnormalities, aiming to establish biomarkers of disease progression. And finally, the study will provide baseline data on clinical measures used to monitor for gene therapy treatment side effects (inflammatory markers, liver enzyme levels, etc.) across the life span of patient with MLIV.